Spinneret production



1965 J. 5. COBB, JR. ETAL 3,279,233

United States Patent 3,279,233 SPINNERET PRODUCTION James Stanley Cobb, Jr., Martinsville, and George Thomas Esry, Stuarts Draft, Va., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corpora- Filed Mar. 28, 1963, Ser. No. 268,795

1. Claim. (CL 72333) This invention relates generally to the. extrusion of polymeric materials and more particularly to the fabrication of a spinneret adapted for use in the spinning of synthetic filaments.

In spinningsynthetic filaments it is essential that spinning Continuity as well as denier uniformity of the filaments be maintained. In order to meet these requirements, considerable effort has been expended in the preparation of spinnerets. Punching and drilling of holes in spinneret plates has reached an advanced stage of development; however, in attaining high efficiency various problems are still encountered.

Utilization of the greatest number of orifices. per unit area of the spinneret plate is desirable. However, in preparing spinneret plates by punching, there is a tendency for the metal adjacent a punched orifice to be displaced thereby distorting the shape of the punched orifice. The displacement of the metal may be alleviated by using a counter-sink, but the counter-sinking operation causes work hardening of the metal making it difiicult to punch accurate holes. In addition, when using punching processes heretofore known, burrs and humps of metal appear on the face of the spinneret. These must be eliminated by grinding and polishing.

Although the drilling of the orifices eliminates many of the just mentioned problems, the orifice wall tends to assume a spiral-like surface configuration which is undesirable. Drilling is also less desirable from a standpoint of accuracy.

It is, therefore, an object of the present invention to provide a method for fabricating spinnerets in which the orifices are accurately positioned with minimum distortion of the spinneret plate. Another object of this invention is to provide a method for fabricating spinnerets in which the surface area of the spinneret plate may be effectively utilized.

The objects of this invention are accomplished by a process which comprises generally the steps of cutting a channel or groove into one face of a spinneret blank, centering a punch in the bottom of the channel, and punching a hole from the bottom of the channel through the blank to provide an orifice communicating with the opposite face of the blank. The resulting hole is formed without significant displacement of the metal in the vicinity of the hole and without the formation of burrs and bumps on the face of the spinneret plate.

In the drawings FIGURE 1 is a spinneret plate which has been grooved and punched in accordance with the teachings of the present invention.

FIGURE 2 is an enlarged fragmentary cross-section taken through a groove and hole which has been punched in the bottom of the groove.

FIGURE 3 is an enlarged fragmentary cross-section taken across a groove showing a counter-sink and a finished hole made according to this invention.

FIGURE 4 is an enlarged fragmentary cross-section taken across a groove illustrating an arcuate shaped groove with a counter-sink and hole.

Referring now to FIGURE 1, the numeral designates a spinneret plate in which a series of concentric grooves 12, 14, 16 and 18 have been cut as the first step in the preparation of the spinneret plate. The grooves may be cut conveniently in concentric circlesas shown in FIGURE 1 by using a lathe or in straight lines using a milling machine. The spinneret plate 1.0 is generally of limited thickness, i.e., 0.05 to about 1.00 inch. The grooves should extend. as deep as necessary to leave the proper thickness for thehole to be punched.

In the next step of the operation, the holes 20. are punched into the spinneret plate Illusing a straight punch. Surprisingly, it has been found that grooving the inner face of the spinneret plate does not reduce the strength to an objectionable degree. When thickness of plate and depth of grooves previously mentioned are used, the spinneret plate is sufficiently strong when supported about its periphery for use in spinning solutions of polymers having viscosities of over poises. It appears that when the grooves are cut in the inner face of the plate in concentric circles, distortion cannot occur at the grooved portions without distortion of the thicker metal portions between the grooves Referring now to FIGURE 2, it is preferred that the groove 22 have straightside walls which form an angle of. about 60. Capillaries or holes 24 are of a relative short length having a ratio of length to diameter from about 1.0 to about 2.0andpreferably 1.25. It isnecessary to have holesofthe same diameter and of the same length in order to produce filaments of uniform denier from a large number of holes. In determining the length of the hole, the counter-sink portion, if. present, is excluded.

As illustrated in FIGURE 3, a small counter-sink 26 may be positioned above hole 28. The counter-sink may be either punched or drilled. Even when a small countersink is punched, little if any, distortion occurs in the spin neret plate since the amount of metal displaced is at a minimum due to the channel.

While it is preferred that the side walls of the groove form an angle of about 60, as iliustrated in FIGURES 2 and 3, variations in the shape of the groove are permissible without sacrificing the advantages of the present invention. As shown in FIGURE 4, the groove 30 may be arcuate in shape. The spinneret plate may include a straightlined countersink 32 in the bottom of the groove. It has been found, however, that when using an angle of about 60 and approximately the same angle for the countersink, stream-line flow is obtained and turbulence is avoided. Utilization of the spinneret plate with the greatest number of holes possible is desired and angles above 60 should be avoided. Greater angles also tend to weaken the spinneret plate. If a counter-sink is to be used above the hole, it is preferred that the bottom of the groove be essentially flat and of about the same width as the countersink. If no counter-sink is to be used, the groove should preferably be only as wide as the diameter of the hole.

As previously indicated the depth of the groove should be controlled to leave a minimum amount of metal through which to punch the holes. If a counter-sink is to be used, the groove should be cut to such a depth as to leave from about 0.015 to about 0.030 inch and preferably about 0.020 inch of metal for both the countersink and the hole. The groove may be of a depth sufficient to leave only about 0.005 inch of .metal through which the hole is to be punched.

In carrying out the process of this invention a spinneret blank is prepared from a suitable meal cg. stainless steel. Concentric V-shaped grooves spaced an equal distance apart are cut into the inner face of the spinneret blank using a milling machine. The grooves have a depth equal to about 65% of the thickness of the blank with the walls forming an angle of about 6 0. Countersinks are then made in the bottom of the grooves by punching to a depth equal to about 70% of the distance between the bottom of the groove and the opposite face of the blank. Holes having a diameter of 0.005 inch are punched through the plate in the center of each of the counter-sinks. concentric grooves. The number of man hours required to prepare the aforementioned spinneret plate are recorded and compared with the man hour requirement for preparing a spinneret plate having the same number of holes and the same plate thickness but using a method of 1 punching counter-sinks and holes Without benefit of the grooves. It is found that by following the process of the present invention only 32% as many man hours are required as required using the other procedure. The spinneret prepared according the the present invention Was 15 used for 500 hours before it was necessary to stop and clean it. The spinneret prepared by punching countersinks could only be operated on an average of 350 hours without cleaning.

Among the advantages accruing from the process of 20 the present invention is the obvious saving of time in fabricating spinneret plates. While the use of channels or grooves connecting holes in a spinneret plate is disclosed in British Patent 723,658 as facilitating flow of the polymer to each hole, the grooving is done after mak- 25 ing the holes. Another advantage of the process of this invention resides in the fixing of one dimensional location of the holes by the groove. The groove not only makes it easier to punch the holes but facilitates accurate locatiOn. 30

It will be recognized that various sizes and shapes in addition to those previously mentioned may be used in The holes are equispaced in each of the 5 preparing the grooves, countersinks, and spinneret orifices. In addition, advantages other than a saving in man hours and increased efficiency in operation which are inherent in the practice of this invention will be readily apparent to those skilled in the art. Accordingly, it is intended that the present invention be limited only by the scope of the appended claim.

We claim:

In the production of spinnerets, the steps of cutting a channel into one face of a spinneret blank, punching a counter-sink into the bottom of said channel, and punching a hole from the bottom of said counter-sink through said blank to provide an orifice communicating With the opposite face of said blank.

References Cited by the Examiner UNITED STATES PATENTS 1,680,073 8/1928 Taylor 29--157 2,350,952 6/1944 Acord 29157 2,383,949 9/1945 Aronson 29l57 2,618,989 11/1952 Cupler 29-157 3,141,358 7/1964 Burke 29--157 3,196,527 7/1965 Bete 29157 FOREIGN PATENTS 922,455 4/1963 Great Britain. 515,678 2/1955 Italy.

79,454 10/ 1955 Netherlands.

CHARLES W. LANHAM, Primary Examiner.

W. H. JUST, Assistant Examiner. 

